There is known a pressure container capable of reserving a high pressure gas or liquid therein. In recent years, a pressure container of a composite structure is proposed, which container is made by covering a thin container (plastic liner) of synthetic resin with a fiber reinforced layer into which resin is impregnated, and then by curing the resin, in order to lighten the pressure container.
For example, a pressure container disclosed in the patent literature 1 is composed of a plastic liner provided with a projected neck portion, a mouthpiece member disposed on the inside of the plastic liner, and a fiber reinforced plastic layer (FRP layer) covering the plastic liner and the mouthpiece member. A seal member of an O-ring intervenes between the plastic liner and the mouthpiece member. The seal member intervenes between an outer peripheral surface of a flange of the mouthpiece member and an inner peripheral surface of the plastic liner.